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NASA's Fundamental Biology Program mandated a goal to provide scientists with a plant growth facility capable of supporting long-duration flight experiments. The Biomass Production System (BPS) takes the first step toward meeting that goal by providing a truly customizable research environment for plant scientists to use on the International Space Station.
Developing technology that enables human life to be sustained in space and understanding the role of gravity in living systems are two major components of the life science vision of NASA.
The BPS is the first plant growth chamber that provides the precise environmental controls required to perform meaningful plant research in microgravity (the near weightlessness condition created inside a spacecraft as it orbits the Earth).
The variables upon which plants depend (light, temperature, moisture, nutrients, and atmosphere) can be independently and precisely controlled in each of the BPS's four plant chambers. These variables can not only be controlled, but they can also be measured while the plants grow from seeds to mature specimens. The ability to control many variables of the growing environment means that stress to the plants is greatly reduced and that microgravity effects can be isolated from routine environmental effects. This versatility makes it easy for scientists to design and carry out a wide variety of experiments on plants in microgravity. The BPS is serving as a sort of "trial balloon" to test the control systems for the Plant Research Unit, which will be a permanent feature of the Destiny Lab on the International Space Station.
The following experiments are taking place in the BPS on orbit as part of Expedition Four.
PESTO (Principal Investigator: Dr. Gary W. Stutte, Dynamac Corporation, NASA Kennedy Space Center)
The objective of the Photosynthesis Experiments and System Testing and Operations (PESTO) experiment is to understand how plant photosynthesis and canopy gas exchange rates are affected by microgravity. For this experiment Dr. Stutte used dwarf wheat, which grows very rapidly. Because plants exchange carbon dioxide for oxygen, they hold the key to providing fresh oxygen for humans to breathe on long-duration spaceflights. Because plants would serve as a critical component of any atmospheric regeneration system needed for long-duration missions, learning how microgravity affects a plant's ability to exchange carbon dioxide for oxygen is essential for creating a successful atmospheric control system.
Two of the BPS plant growth chambers will be devoted to the PESTO experiments. They were launched with 11-day old and 3-day old plants. A third BPS plant chamber is shared by the PESTO experiment and the TVT experiment led by Dr. Robert Morrow. In this third chamber the PESTO wheat plants (launched at 5 days old) are subjected to a variety of relative humidity and temperature settings to study the various settings' impact on photosynthesis in microgravity. Three growth cycles of plants will occur while the chambers are in microgravity. Plants will be harvested on the ISS and new plants started in the chambers so that several plant life cycles can be studied.
TVT - Technology Verification Test (Principal Investigator: Dr. Robert C. Morrow, Orbital Technologies Corporation)
Running all the BPS controls through their paces is the primary goal of this series of tests. Collecting data on the performance of the various subsystems will help engineers create robust subsystems for the Plant Research Unit and reduce the risks associated with developing cutting-edge spaceflight hardware.
Wheat (Triticum aestivum v. Apogee) and rapid cycling Brassica rapa (Brassica rapa v. ASTROPLANT) are the two plant species that will be used for the TVT. The function of these test plants is to provide different biological loads on the BPS to make sure it does its job in microgravity. Wheat was selected as a test plant because it produces a large amount of green matter, which in turn will create a high humidity load on the BPS. The Brassica rapa (member of the same family as cabbage and broccoli) grows rapidly through flowering and seed development, providing a good test for the BPS's ability to handle a developmentally complex plant. Additionally, because the Brassica requires the crew to pollinate it, the crew will be able to evaluate how easy it is to open the BPS and access the plants in its chambers. And finally, because Brassica is a somewhat "messy" plant, it is a perfect test case for the BPS air filtration system.
Experiment OperationsThe BPS was flown to the International Space Station on Shuttle STS-110, launched 08 April 2002. Once on board the Station, the BPS was installed in EXPRESS Rack 4.
The current duration of this experiment is 66 days. At launch the first set of plants were 3 days of age (Chamber 1), 11days of age (Chamber 2), 5 days of age (Chamber 3), and 4 days of age (Chamber 4). All these plants will be harvested on orbit and root modules (the container of "soil" for the plants) that have been pre-planted with seeds will replace them. A total of seven additional root modules will be primed, or started by "watering," on orbit. The last set of root modules will be returned to Earth with live plants. Wheat plants for chambers 1, 2, & 3 will be germinated and harvested on-orbit. The total number of root modules harvested for this flight experiment is 11. Another 11 modules will be harvested as part of the ground control experiment that will be conducted at Kennedy Space Center.
On-orbit harvests, root module priming, and pollination activities are all conducted by the ISS crew. The crew member removes the desired plant growth chamber and attaches it to a work surface in the laboratory module. During harvest operations, plants are cut at the base and placed in a preservative or put in an on-board freezer unit. Priming of root modules is done by injecting water into a root module to wet the seeds and then removing air from the root module fluid loop before placing it back in the BPS. Pollination of Brassica plants is done by moving pollen from flower to flower using "beesticks" made from the thorax of bees.
The BPS reports on the environmental conditions that the plants are living in every minute. It also takes video pictures of the plants in each chamber every two hours. All these data are transmitted to Earth every five minutes so that the scientists can keep careful watch over their experiments and make changes to the set points, if they desire. The BPS can control temperature within +/-1C between 20C and 35C. The relative humidity can be maintained within +/- 5% of the set point in the range of 65% to 90% (depending on the temperature setting). Light levels and CO2 levels are also controllable. The BPS removes ethylene gas (a gas produced by plants during their normal growth cycle) so ethylene levels do not get high enough to impact plant development.
The primary function of the crew during the BPS experiment is to conduct plant harvests, start new root modules, and to pollinate the Brassica plants. The crew also collects gas and liquid samples and performs daily status checks on the BPS hardware. As part of this experiment, the crew is providing crew assessments and video for the various functions they perform.
A second BPS unit is being operated on the ground at the Kennedy Space Center as a control for the BPS flight experiment. This experiment is called the BPS Ground Control and was begun two weeks after the BPS flight. The two week delay allowed enough time to gather and record the environmental conditions (temperature, humidity levels, etc.) on the Space Station experiment and load them into the Ground Control unit so that the ground experiment can run in as close to the same conditions as possible to those on the Space Station. All procedures done to the BPS experiment on the ISS will be repeated in an identical fashion on the Ground Control unit. The BPS will be returned to Earth on Shuttle STS-111 in early June. The plants that return from orbit will be harvested at the Kennedy Space Center. The harvested plant material will be sent to various laboratories around the country for analysis. Gas and fluid samples collected on-orbit and from the ground control experiment will also be gathered and sent for analysis.
BPS's history began over 15 years ago.
1985 Tom Crabb, Eric Rice and Ron Teeter, ORBITEC's eventual founders, work with the University of Wisconsin to establish a NASA commercialization center in Wisconsin.
1986-88 ORBITEC founders and future employees support development of plant growth technologies and four flights on the Space Shuttle through the commercialization center.
1988 Crabb, Rice and Teeter found ORBITEC.
1988 ORBITEC signs agreement with the University of Wisconsin to become the commercial agent for plant growth hardware.
1992 ORBITEC is included as a subcontractor to support McDonald Douglas as provider of plant growth system hardware as part of Centrifuge development.
1994 ORBITEC submits and wins an Small Business Innovation Research (SBIR) contract to develop the next generation plant growth system with the University of Wisconsin as a partner. This was the birth of BPS.
1995 ORBITEC aligns BPS specifications with those required by NASA for its Plant Research Unit and wins a SBIR Phase II contract to further develop the BPS.
1996 BPS team works very hard to meet the imposed deadline. A kickoff meeting at Kennedy Space Center is held in January. A design review takes place at ORBITEC in April 1997. Working BPS hardware is presented by ORBITEC in September 1997.
1997 BPS Phase III contract is awarded to ORBITEC for a short duration flight on the Shuttle STS95 for flight in 1998 as a development unit for the Plant Research Unit.
1998 BPS flight is changed from a Shuttle-only flight to a longer durationmission on the International Space Station. The BPS is to be installed in the EXPRESS Rack on the Space Station after launching on Utilization Flight 1 in 1999.
1999-0 After changing several times, the BPS flight schedule is finally anchored on Increment 8a.
2000 Plant Research Unit development contract is awarded to ORBITEC. This is the largest Phase II contract ever awarded by NASA to a small business.
2000-01 BPS passes several science, verification, and mission tests.
2002 BPS is launched 8 April 2002 for 65 day mission on the Space Shuttle and the International Space Station.
The study of plants in space can advance the fundamental knowledge of plant biology. Generation of new knowledge increases the likelihood of developing useful applications in medicine, agriculture, biotechnology and environmental management. Space is the only environment where fundamental processes can be studied without overriding gravity effects. This knowledge can help unravel the precise control mechanisms involved in dictating plant form, structure, and function. Understanding these basic processes may lead to the development of new products and increased plant productivity.
Knowledge gained from studying plants growing in microgravity will help us create plant growth systems that can provide food for the crews of the long-duration space missions that will be needed to meet NASA's mission of "exploring the Universe and searching for life." What we learn about plant growth in space may also help us to understand and protect plants here on Earth.
On Earth plants serve as systems capable of removing excess carbon dioxide from the air and replenishing the atmosphere with oxygen. Plants also transport water from their roots to supply themselves with nutrients and to support their growth. This process is called transpiration. Transpiration results in nutrient rich water being converted to purified water as it evaporates. The process of transpiration thus provides an excellent means of purifying water. Because both pure water and breathable air are crucial necessities for spaceflight, studying the effect of microgravity on a plant's ability to complete these two processes-exchanging oxygen for carbon dioxide and purifying water-can have invaluable, positive impact on designing systems for future spaceflight missions.